Water-resistant alkaline silicate compositions



Patented Mar. 6, 1934 WATER-RESISTANT ALKALINE SILICATE CGMPOSITIONS Louis Leonard llarson, Wilmington, Del., assignor,

by mesne assignments, to The Grasselli Chemical Company, Cleveland, Ohio, a corporation of Delaware No Drawing.

9 Claims.

The prescnt'invention relates to novel compositions of alkali metal silicates in admixture with substances which impart a considerable desurfaces of other materials to which the silicates are, applied." l

These films and bonds are mainly formed by partial dehydration, such as evaporation or absorption of the water of the silicate solution, whereby a compositionof hydrated silica and alkali silicate is formed.

Such compositions are soluble in water and though the solvent action of water thereon is slow, the films or. bonds are not highly water resistant. It is on the other hand well known that acids and salts precipitate silica from alkali metal silicates, whereby the adhesive and film forming properties of the silicate solutions are completely destroyed. I

I have found thatcomplex ammine compounds of metals when dissolved in solutions of alkali metal silicates do not precipitate silica and that on partial dehydration such solutions form waterreslstant films and my invention is directed to the adhesive or coating compositions comprising solutions ofalkali metal silicates containing complex ammine compounds of metals and their applications for adhesive, coating and other purposes in which the adhesive film forming'properties of alkali metal silicates is made use of.

While I am not prepared to give a theoretical explanation for the fact that complex metal am-.

metal salts gradually react to form insoluble silicates which protect the silicate adhesive films 50 against the solvent action of water. 1

The adhesive and water resistant properties of films and coatings obtained from solutions of alkali metal silicates and ammine complexes are not impaired by the presence in the solutions of 5 other substances intended to modify further Application January 2, Serial No.'584,567

cates to form a strong bonding film on or between the properties of the'fllms. I can add to the silicate-ammine solutions thickening agents, water repellents, water insoluble adhesive substances, flexibility modifying agents, such as glycerine and others, or substances which com-' bine several of these properties. The films and coatings or adhesive bonds produced from such modified silicate-ammine solutions have an excellent water resistance besides the particular properties derived from the presence of the particular modifying agent.

\ The metal ammines which I have found to give water resistance to silicate filins without precipitating silica from silicate solutions and which do not impair the adhesive properties ofsilicate films,- are the complex addition compounds of metal compounds with ammonia or its equivalents such as amines. These compounds are also known by the term ammoniates. Amines of practically every heavy metal are known. They exist for the various valence values of-the metals, such as there are cobalto and cobalti ammines, cuprous and cupric ammines, etc. Am-

monia and amines add themselves to metal comthe metal silicates are insoluble in water. The

. addition of a metal salt of the first order to an alkali metal silicate precipitates therefor an insoluble silicate. and used technically with various ratios of Na2O to SiO2 which range from the meta silicate in which the ratio is 1:1 to silicates with a ratio of 1 NazO to 4 or more SiOz.

The excess silica contained in the high ratio silicate solutions is usually considered'to exist in a colloidal state. When electrolytes in substantial amounts are added to such solutions, the colloidal bond is broken and hydrated silicic acid precipitated.

Substantial amounts of metal ammines can be added to soluble silicates without precipitatingmetal silicates or breaking the colloidal bond of Alkali metal silicates are known tions. This holds true for even concentrated,as

eight to ten months.

for instance, 35 to B sodium silicate solutions, and such' solutions containing up'to and even more than 20% of metal ammines based on silicate solids have remained stable for more than When the ratio of $102 to N820 exceeds about 3.8 there is, however, a tendency for the metal ammin'esto gradually decompose the silicate solutions, the same as ordinary or neutral electrolytes will do immediately but with sodium silicates as used for adhesive purposes which have ratios from 1:2 to 1:35, this tendency for decompositionis not noticeable, and the invention is particularly directed to sodium silicates of this range.

' The general procedure'for .modifying silicate solutions in accordance with my invention is as follows:

An aqueo'us solution of a complexa e compound is formed by dissolving a me salt in water and then adding suflicient aqua ammonia or an amine to first precipitate and th n redissolve the metal. hydroxide to form a solu le ammine complex. This solution-is then added slowly to the sodium silicate solution withthorough agitation. There is in some instances a precipitate formedon the'mixing of the two solutions and when freshly prepared the modified silicate contains in most cases a small amount of finely divided precipitate suspended in solution. These precipitates dissolve, however, after the solution has aged for a couple of hours. Too rapid addition of the complex ammine solution or insuf ficient stirring of the silicate solution results in gelatinous precipitates which dissolvev in time, but their solution is very slow. Care must, there- .fore, be taken that the addition of the ammine and the stirring be regulated so as to form as little precipitate as possible. The so obtained modified silicates are perfectly stable on standing for a long .time. They are adjusted to the desired viscosity and used in the same manner as straight sodium silicate solutions for adhesive or coating purposes.

While a large number of complex metal ammines have been tested by me, I found that cuprio, zinc and cadmium ammines, particularly those derived from'the sulfates, are particularly practical from an economical standpoint for the production of modified sodium silicates which produce water resistant adhesive films, bonds and coatings.- g

The amounts of metal ammines in sodium silicate solutions of 1 Na2O:3.2 SiOz ratios which give water resistant films were found, for instance, to correspond to from 0.5% to 21.0% CuSO4 based on the sodium silicate solids of the solution. Slightly-higher amounts of cupricammino sul-'- fate could be incorporated, but it is not recommended that the amount of cupricammino-salt be increased substantially above the figure given. As a matter of fact, it is best in most instances to use cupricammino sulfate in amounts corresponding to from 9 to 12% copper sulfate. With silicates of a 1:2.4'rati'o amounts of copper ammine sulfate corresponding to 35% copper'sulfate have been.successfully incorporated into the sili-.

cate solution without decomposition.

In the case of cupricammino-chloride. 7.7% CuClz was found a very convenient amount to produce a stable modified sodium silicate which will form a water resistant film, etc.

In the case of a 2.4 sodium silicate the maximum sodium silicate solution of ratio 123.2. The soluof cupricammino-chloride which could beincorporated into the silicate was found to correspond to approximately 23% CuCla.

- The amounts of zincammino-sulfate, cadmiumammino chloride were found to be within the same orders of magnitude. Thepreferred concentrations and the approximate limiting concentrations of ammonia were found I as follows:

The I preferred concentration of ammonia is the amount required to form the soluble complex ammine with themetal salt in aqueous solution. In molar equivalents this corresponds approxi-Lv mately to 4.45 mols of NH: to 1 mol of 011804, 5.65 mols of NH: to l'mol of CuClz, and 7.3 mols of NH: to 1 mol of ZnSOr. Sodium silicate solutions were successfully modified, using about 2.25 mols of NH; to 1 mol of CuSO; or CuCla. Both these are about the lower limits of concentrations to be recommended, for the reason that these modified silicates were not stable for a period greater than six weeks. An excess of ammonia is not harmful, but is unnecessary and offers no V practical advantages.

The following area few examples showing the application of my invention to, the production of modified sodium silicate solutions useful for the formation of water resistant-adhesive films, coatings or bonds: 4

Example 1:-45.8 parts of an aqueous solution of copperammino-sulfate as was obtained by mix-' ing 14.4 parts of blue vitriol with 16.5 parts of water and 14.9 parts of aqua ammonia of sp. gr. 0.90, was added slowly to 200 parts of a 42.5" B.

tion was diluted with 14.6 parts of water to bring its viscosity to the viscosity of the original sodium silicate'solution. The modified silicate has good adhesive properties and a more rapid rate of set than the original silicate. The water resistivity 5 of its film as an adhesive by the following:

Chip-board joints formed by application of the silicate and agedfor seven days at room temperature had a life of four days to complete failure under heavy tension in water, compared with twenty minutes lfe for the straight sodium silicate controlled joints. Bond writing paper joints made and tested as above had a lifeof three days in water, compared, with'five minutes forthe straight sodium silicate controlled joints. The modified silicate solution was perfectly stable after eight and a half months of age.

Example 2:23.4 parts of a solution of a com plex coppera'mmino-sulfate obtained by dissolving 7.2 parts of blue vitriol. 7.7 parts of water and 8.5 parts of aqua ammonia sp. gr. 0.90, were for paper is illustrated added slowly to 200 parts 35 B. sodium silicate solution of ratio 1:32, with good stirring and diluted with 17.4 parts of water. An additional 35 amount of copperammino obtained from 36.6 parts of a 20% aqueous solution of blue vitriol was then added and the viscosity adjusted by dilution to that of the original silicate. .This solution was stable for at least six weeks and showed an eyen better water resistance than films obtained from the modified silicate of Example No. 1.

Films produced from such modified sodium silicate solutions when produced for instance, on glass, show a considerably greater resistance to water than straight sodium silicate films; Such films, when broken away from the surfaces on which they were formed, were only slightly dissolved after two months sojourn in water whereas 15 when made from straight sodium silicate they would dissolve in. a few minutes.

Example 3:--l2.7 parts of soy bean meal was dispersed by grinding in 22.3 parts of water and 65 parts of a 38.5% solution of sodium silicate having a ratio of lNazO to 3.2 $102. When the soy bean meal was well dispersed, 194 parts of the silicate solution, 5.1 parts of wood flour, and 7.6 parts of water were added. The solution was next modified with a solution of cupricamminosulfate consisting of 14.3 parts of blue vitriol, 15 parts of aqua ammonia of 0.90 sp. gr., and 41.3 parts of water. The cupricammino-solution was added slowly with thorough agitation to the modified silicate solution. Then 13.1 parts of blown China-wood oil contafning 0.13 parts of the sodium salt of petroleum sulfonic acids was added slowly with thorough agitation of the solution.

The high water resistance of an adhesive having the above composition isillustrated by the following data: Chip-board joints glued with the composition and aged for seven days at room temperature had a life of forty-seyen days to complete-failure under tension in water, compared with twenty minutes life for the joints which had been glued with unmodified sodium silicate.

hesive properties, and a more rapid rate of set than the original silicate.

For example, a film on glass of this modifiedsilicate dried .to tackfree state in three minutes, compared with eight minutes for the original silicate. The so obtained film when flaked from glass and placed in water had not been completely dissolved after. four months ofi contact. Chip-board joints of this adhesive had a life in water of 2 days, compared with 30 minutes for control joints of the original silicate. This modified silicate solution has shown perfect stability-for four months.

The above examples are merely given to illus- .trate the general procedure, the amounts, the

and this emulsion added to the modified sodium silicate solution. These hydrocarbons are easily incorporated into the sodium silicate solutions and though the emulsions have a decided tendency to cream in the absence of agitation, the

creamed phase, if formed, can easily be redispersed by stirring. The tendency of the emulsion to cream is greatly reduced by the presence of wood flour in'the emulsion; for instance, 10% of the sodium silicate solids content when using amounts of parafline up to 20%.

' water;

- stances.

The properties of these modified sodium silicateadhesives are as follows:

They have good adhesive properties. Their rate of set is equally as rapid as that of the untreated sodium silicate. They have proven stable for several months. Their films on glass when dry have a high contact angle with a drop of Chip-board joints glued with a sodium silicate copperammino compound paramne wood-flour composition and aged at room tem pcrature for one week had a life of 10 days to complete failure when placed under tension in water, compared with the four days life of a sim ilar copperammino-sulfate-sodiurn silicate solution. It will be seen that the water resistance has been more than doubled by the incorporation of a water repellent and wood flour, the latter acting both as a: thickening agent and as a stabil'zlng agent for the emulsified parailine.

At normal water content the above composition has a pastelike consistency. As an example, a' sodium silicate-copperammino-parafline composition of paste-like consistency was prepared by adding to the composition described under Example I a 50% water emulsion of parafifine in'an amount equal to 50% paraifine based on the silicate solids. Thefilm of the composition on glass was very water repellent, continuous and did not crack orpeel and is particularly adapted in the field ofcoatlngs and sizes; The composition can, of course, be modified within wide limits, both as to the water repellent and thickening'agent and as to the composition of the modified silicate. The composition can likewise be modified further by the addition 'of pigments which may serve .both as thickening agents or dispersing agents for the paraffine, etc., and impart to the compositions a distinct color.

The composition can, for instance, be used as a substitute for asphalt in the paperboard industry.

Instead of the water repellent substances, or in addition to them, I can also incorporate in my novel sodium silicate compositions substances which will add to the adhesive properties of the films, particularly water insoluble adhesive sub- Of these I can -mention drying oils, such as blown China-wood oil, blown linseed oil. rubber latex, particularlyin the concentrated form, and many other water insoluble adhesives.- Here again I may use thickening agents which in addition act as stabilizing agents for the ad-- hesive, and I have incorporated into my modified s licate solutions, besides the China-wood and linseed oils, substances, such as wheat flour, starch, pectin, salts of alginic acid, kelp flour, etc.

In another modification of my metal ammine salt.oontaining sodium silicate solutions I add protein containing meals to the solutions, such as soy bean meal or peanut meal in amounts up to 50% based on the silicate. solids. The addition of these protein containing meals to the modified silicate solutions influences the rate of set, which is retarded by the addition of the protein substance, whereas the metal ammine rather speeds up the rate of set. It is, therefore, possible to prepare water resistant sodium silicate adhesives varying greatly in their rate of set. The working life of a sodium silicate adhesive solution modified with a complex ammine of copper, zinc, cadmium, etc., and a protein containing meal varies from one-half to mine is increased. v

Qasemcreams rapidly'from solutions where a casein preparation solubilized in water with ammonium hydroxide is added'to a sodium silicate-'ammine solution. I found, however, that the further addition of soy bean meal stabilizes the solution of silicate.

Casein was, for instance, incorporated in amounts up to based on the silicate solids casein in the modified. sodium into a sodium silicate solution containing of soy bean meal and"1 2% copper sulfate asthe ammine complex.

The high water resistance of compositions con taining soy bean meal, casein, etc. was shown by the following tests: v 7 1 Chip-board joints glued-with ammine modified sodium silicate and a protein meal and aged at rooxntemperature for one weekwere still in good condition after 50days of immersion under tension in water. -This compares with the life of metal silicate with a metalammino, salt.

2.' As an adhesive and coating composition an aqueous solution comprising the reaction product obtainedby mixing a solution of sodium silicate with a metalammino-salt.

3. As an adhesive and coating composition an aqueous solution comprising the reaction prod- .l uct obtained bymixing a solution of sodium silicate'with a metalan'imino sulfate.

v 1,949,914 v creases as the concentration of the complex am- -4. As an adhesive and coating composition an aqueous solution comprising I the reaction product obtained by mixing a solution of sodium silicate with a metalammino chloride. 5., As an adhesiveand coating composition an aqueous solution comprising the reaction product obtained by mixing a solution of sodium silicate' of a NazO:SiOz ratio between 1:1 and 123.5 with a metalammino salt or the group oi metals consisting of copper, zinc andcadmium.

6; As an adhesive and'coating composition an aqueous solution comprising. the reaction product obtained by mixing a solution of sodium silicate of a NazO:SiOi ratio between 1:1 and 113.5.

with a solution of a copperammino salt.

7. As an adhesive and coating composition an aqueous solution comprising the reaction product obtained by mixing a solution of sodium silicate of a NaOzSiO: ratio between 1:1 and 1:3.5 with a solution of a copperammino sulfate.

8. As anadhesive and coating composition an aqueous solution comprising the reaction product obtained by mixing a solution of sodium silicate, of a Nazozsioa ratio between 1:1 and 123.5 with asolution of a zincammino salt. 1 v

9. As an adhesive and coating composition an aqueous solution comprising the reaction prodnot obtained by mixing a solution of sodium silicate of a Na2O:SiO2 ratio between 1:1 and 1:3.5 wit-h a solution of a copperanimino sulfate, the amount of copperammino 's sponding to from 0.5 to 2 1% uSO4 based onthe sodium silicate solids used.

LQUIS L. LARSON.

ate used -corre- 

